Re: [Qemu-devel] unix sockets for qemu

[Daniel P. Berrange]

On Tue, Feb 26, 2013 at 05:31:04PM +0100, Stefan Hajnoczi wrote:
> On Mon, Feb 25, 2013 at 07:02:30PM -0600, address@hidden wrote:
> > The associated file contains a README that will guide you through the
> > experiment that shows the difference between unix socket carried pings:
> > 0.7ms and inet carried pings: 40ms!!!
> 
> There is no fundamental reason for inet sockets to have a 40 millisecond
> round-trip time on localhost.  I remember from years ago that Solaris
> "fuses" localhost inet sockets and bypasses TCP for them.
> 
> Adding a call to socket_set_nodelay() net/socket.c might help.

Yes, I'm pretty sure it will be the nagle algorithm that is causing this
delay. Localhost IP sockets can round-trip ICMP packets in <0.1 ms

If we don't want to disable nagle by default here, we could at least
make it a configurable option for people.

Regards,
Daniel
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